Where 'dispensation' appears in God's Word, it never means 'a period of time'. Nor does the Greek word behind it carry the notion of a segment of time.
God has given us certain gifts and the space to use them. He expects us to use them properly in service to Himself and the Body, and requires an accounting.
As one uses the power provided by God's Holy Spirit, even one who has previously failed miserably can rise to astounding levels of spiritual competence.
Jesus Christ has full control of the church. Everything of consequence, including the development of our character, is engineered by Him.